This patent application claims priority based on a Japanese patent application, 2000-222926 filed on Jul. 24, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a testing apparatus for testing an electron device. More particularly, the present invention relates to a testing apparatus, which has an apparatus for a high current testing, and an apparatus for a low current testing.
2. Description of the Related Art
FIG. 1 shows a conventional testing apparatus 100. The testing apparatus 100 comprises a direct-current testing apparatus 10 for a high current and one or more direct-current testing apparatus 20a . . . 20n for a low current. The direct-current testing apparatus 10 is an apparatus, which supplies higher current than the direct-current testing apparatus 20a . . . 20n. The electron device 30 to be tested has a plurality of electrodes, each of which is connected to corresponding switches 12-1 . . . 12-n, switches 14-1 . . . 14-n, switches 16-1 . . . 16-n, switches 18-1 . . . 18-n. Switches 12-1 . . . 12-n and 18-1 . . . 18-n are each connected to a sense line 22 and a force line 26 of the direct-current testing apparatus 10. As shown in FIG. 1, switches 14-1 . . . 14-n are each connected to corresponding sense lines 28a . . . 28n of the direct-current testing apparatus 20a . . . 20n and switches 16-1 . . . 16-n are each connected to corresponding force lines 30a . . . 30n of the direct-current testing apparatus 20a . . . 20n. Further, the testing apparatus 100 has a measure line 24 selectively connecting the direct-current testing apparatus 10 and direct-current testing apparatus 20a . . . 20n. 
The testing apparatus 100 performs a voltage applying current measuring test, which applies predetermined voltage on an electron device 30 to measure a current supplied to the electron device 30, or performing an electric current applying voltage measuring test, which supplies predetermined electric current to the electron device 30 to measure a voltage applied on the electron device 30.
The testing apparatus 100 will be explained below using a voltage applying current measuring test as an example. When a high current must be supplied to the electron device 30, the direct-current testing apparatus 10 applies voltage to the electron device 30 through the force line 26. The voltage applied to the electron device 30 is fed back to the direct-current testing apparatus 10 through the sense line 22. The direct-current testing apparatus 10 adjusts the voltage applied to the electron device 30 to the predetermined voltage based on the fed-back voltage. Moreover, the direct-current testing apparatus 10 detects the current supplied to the electron device 30 when predetermined voltage is applied to the electron device 30. The testing apparatus 100 judges the quality of an electron device 30 based on the detected current.
When a low current must be supplied to the electron device 30, the direct-current testing apparatus 20a . . . 20n applies voltage to the electron device 30. The voltage applied to the electron device 30 is fed back to the direct-current testing apparatus 20a . . . 20n. The direct-current testing apparatus 20a . . . 20n adjusts the voltage applied to the electron device 30 to predetermined voltage based on the fed-back voltage. Moreover, the direct-current testing apparatus 20a . . . 20n detects the current supplied to the electron device 30 when predetermined voltage is applied to the electron device 30. The testing apparatus 100 judges the quality of an electron device 30 based on the detected current.
When the testing is performed by applying voltage to the electron device 30 from the direct-current testing apparatus 10, the corresponding switches 12-1 . . . 12-n and 18-1 . . . 18-n are switched-on, and the switches 14-1 . . . 14-n and 16-1 . . . 16-n are switched-off. When the testing is performed by applying voltage to the electron device 30 from the direct-current testing apparatus 20a . . . 20n, the corresponding switches 14-1 . . . 14-n and 16-1 . . . 16-n are switched-on and the switches 12-1 . . . 12-n and 18-1 . . . 18-n are switched-off.
The electron device 30 has a plurality of electrodes to be tested, and the testing apparatus 100 has the direct-current testing apparatuses 20 for each electrode. The testing apparatus 100 performs testing by choosing the desired electrodes using the switches 12-1 to 12-n, the switches 14-1 to 14-n, the switches 16-1 to 16-n, and the switches 18-1 to 18-n, which are provided for each plurality of electrodes. Moreover, the testing apparatuses that perform other tests are also connected to the plurality of the electrodes of the electron device 30.
The testing apparatus 100 mentioned above switches-off switches 12-1 . . . 12-n, when the testing apparatus 100 is separated from the electron device 30. Each of the switches has a floating capacity, called off capacity. Since the off capacity is large, the value measured by the testing apparatus that performs other test is affected when the switches 12-1 . . . 12-n, 14-1 . . . 12-n, 16-1 . . . 12-n and 18-1 . . . 12-n are switched-off. Thus, it was difficult to test the electron device 30 with sufficient accuracy. Therefore, it was desired to reduce the off capacity of the switch that separates the testing apparatus 100 and the electron device 30.
Therefore, it is an object of the present invention to provide a testing apparatus which overcomes the above issues in the related art. This object is achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
To solve the above issues, according to the first aspect of the present invention, a testing apparatus for testing an electron device comprises a first supply unit that supplies a first current to the electron device; a first feedback circuit which feeds back voltage applied to the electron device to the first supply unit; a first switch which switches to whether or not connect electrically the electron device to the first feedback circuit; and a second supply unit that supplies a second current to the electron device, the second supply unit being separated from the electron device by the first switch.
In the first aspect of the present invention, the first supply unit may adjust a voltage or a current to be supplied to the electron device based on the voltage, which is fed back by the first feedback circuit. Moreover, the testing apparatus may further comprise a second switch that switches to whether or not connect electrically the first supply unit to the electron device. The testing apparatus may further comprise: a third switch that selects to whether or not connect electrically the first feedback circuit to the first supply unit; and a fourth switch that selects to whether or not connect electrically the second supply unit to the electron device via the first switch. The second current may be lower than the first current.
The first feedback circuit may have a voltage follower circuit that outputs a voltage substantially equal to an input voltage, and the input impedance of the voltage follower circuit is higher than the output impedance of the voltage follower circuit. The second supply unit may have a supply source that supplies the second current to the electron device and a feedback path that feeds back the voltage applied to the electron device to the supply source; and the supply source adjusts the voltage or current to be output to the electron device based on the voltage fed back by the feedback path.
The electron device may have a plurality of electrodes; and the first supply unit may supply the first current to each plurality of electrodes; and the testing apparatus may further comprise: a plurality of the first feedback circuits, each of which feeds back voltage applied to the plurality of electrodes to the first supply unit, respectively; a plurality of the first switches, each of which switches to whether or not connect electrically the plurality of electrodes to the plurality of first feedback circuits; and a plurality of second supply units, each of which supplies a second current, which is lower than a current that is supplied by the first supply unit, to each of the plurality of electrodes, and the plurality of second supply units are separated from the plurality of electrodes by the plurality of the first switches, respectively. The testing apparatus may further comprising a judging unit that judges quality of the electron device based on the detected voltage or current supplied to the electron device detected by one of the first supply unit and a plurality of the second supply units.
According to the second aspect of the present invention, a testing apparatus for testing an electron device comprises: a first supply unit that supplies a first current to the electron device; a supply line that connects electrically the electron device and the first supply unit, and the first current flowing therethrough; a first feedback circuit which feeds back voltage applied to the electron device to the first supply unit; a second switch provided on the supply line which switches to whether or not connect electrically the electron device and the first supply unit; and a second supply unit that supplies a second current to the electron device, the second supply unit being separated from the electron device by the second switch.
The testing apparatus may further comprise: a fifth switch that selects to whether or not connect electrically the first supply unit to the electron device via the second switch; and a sixth switch that selects to whether or not connect electrically the second supply unit to the electron device via the second switch. The second current may be lower than the first current.
The electron device may have a plurality of electrodes; and the testing apparatus further comprising: a plurality of the supply line that connects electrically the electron device and the first supply unit, and the first current, which is supplied to each of the plurality of electrodes by the first supply unit, flowing therethrough; and a plurality of first feedback circuits, each of which feeds back voltage applied to the plurality of electrodes to the first supply unit, respectively; a plurality of the second switches provided on the supply line, each of which switches to whether or not connect electrically the plurality of electrodes to the first supply unit; and a plurality of the second supply units, each of which supplies a second current, which is lower than the current that is supplied by the first supply unit, to the plurality of electrodes, and the second supply units are separated from the plurality of electrodes by the plurality of second switches.
This summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the above described features. The above and other-features and advantages of the present invention will become more apparent from the following description of embodiments taken in conjunction with the accompanying drawings.